The Spares
by revive-the-books
Summary: While Sherlock is busy with a case, John comes across a mystery of his own.
1. Chapter 1

**AN: Hello Internet. What's up? So I have a pre-fall fic for you guys. I hope you like it, and let me know what you think (a.k.a. please give me a review!). :]**

**Disclaimer: No, I do not own Sherlock.**

Chapter 1

John Watson was walking through downtown London, hoping for some fresh air. His flat mate, Sherlock Holmes, was experimenting with human decay again, filling the flat with the smell of death, and John had been anxious to get out of there. He was walking down a row of shops when a sudden feeling overcame him and sent shivers down his back. He turned around, sensing a pair of eyes on him. He was positive it wasn't Sherlock because almost nothing could tear him away from one of his experiments.

Finding nothing out of the ordinary, John continued walking and came across a small grocery store. _Might as well go and get some milk while I'm out,_ he thought. _It's not like Sherlock was actually going to go out and get some himself._ John entered the store and a little bell tinkled above his head. He looked around and saw no one in the store, so he proceeded to walk the four metres that were between him and the small refrigerator in the back of the shop. He opened it and started to pick up a small carton, but it was lighter than he had anticipated. His hand lifted too quickly and slammed into the top of the refrigerator, causing him to drop the carton, which landed facedown, revealing a hole cut into the back of it. John shook his hand to bring down the pain. A shiny object caught his eye, so he bent down to investigate the carton.

He picked up the carton and shook the object into his hand. It was a key. The key seemed to be brand new, considering that there were no scratches on it. John turned the key over in his hand and saw something engraved on the key.

221B


	2. Chapter 2

**AN: So here's Chapter Two. Please review! It would be appreciated :]**

**Disclaimer: For this purpose Sherlock belongs to BBC**

Chapter 2

John rushed home once he made his discovery. He burst in and placed the key on the table where Sherlock was working.

"Sherlock?" he asked. The other man hadn't even looked up from the disembodied arm he was working on. "Sherlock!" John said, raising his voice.

"John, I told you that you weren't to talk to me. I'm on an important case," Sherlock said, irritation was evident in his tone, as he injected something into the arm.

"When did you tell me that?" John asked.

"About twenty minutes ago. Now, shut up."

John sighed. "Sherlock, I've been out for at least two hours. Sooner or later you are going to notice." Sherlock didn't reply, so John directed the conversation towards the key. "Have we got any spares for the apartment?"

"Of course not, John. Don't be ridiculous. Now stop talking before I take one of your arms," Sherlock went back to his work, leaving John to his thoughts. _Maybe I could do this on my own. I've been living with one of the most brilliant brains on the planet. Surely I must have picked up a few trade secrets by now. What would Sherlock do now?_ He grabbed his coat and exited the apartment for the second time that day, taking the key with him.

He hailed a cab and immediately went to St. Bart's. He hesitated outside the lab door, where he could hear Molly working on something, wondering whether or not this was something worth bothering her for. After a while he pulled the door open and entered the lab.

"I'm a little busy at the moment, Sherlock," she said without looking up when John entered the room. "So you best be turning around and leaving."

"Sorry," John said, causing her eyes to snap up and meet his. "It's just me, but I'll come back later if it's that much of an inconvenience."

"Oh, sorry," she said, blushing deeply. "I just thought that... oh never mind. It's okay John, you can stay. What can I do for you?"

John put his hand on the doorknob and furrowed his brow. "I have something I wanted to take a closer look at, but I think I'll just come by later."

"Nonsense John," a deep voice called from behind the door. John sighed and opened it, revealing the consulting detective. "You are obviously worried about something, so it would be better for your dear conscience to have it taken care of as soon as possible."

Sherlock Holmes entered the lab, removed his trench coat and scarf, and handed them to Molly. "Molly, be a dear and take care of these for me," he said as he walked around the lab, picking up things he wanted to use.

"I'm not a deer, Sherlock," Molly mumbled as she tossed the items into a corner of the room, then swiftly walked by John, and out the door.

"What happened to your decaying arm experiment?" John asked, as he approached the tall man.

"I had to come down to the morgue to gather more body parts, when I stopped just outside the door and happened to hear your conversation," Sherlock said, holding his hand out for John to give him the object of concern. John sighed and dropped the key into his hand.

When Sherlock saw the key glisten in his hand, he smirked and looked up at John. "A spare?" he asked. "This is what has you in such a tizzy?"

"Well, I found it," John began.

"In a small shop that you assumed was abandoned, yet you still had an odd feeling of being watched," Sherlock finished, gently placing it under the microscope he had selected.

John looked at him hesitantly. "Were you following me again?" he asked.

"No," Sherlock replied. "But I know what happened because that is the exact way I found this," Sherlock pulled a different key out of his pocket that was wrapped in plastic.

"Is that another spare to our flat?" John asked.

"No. It's to a building across town. I haven't been able to get in yet, but it seems intriguing, doesn't it?" he asked, gazing into the microscope.

"I don't really know about intriguing," John said, leaning against the lab counter. "It seems more like someone has a key to our flat."

"Yes, and that is what makes it intriguing," Sherlock said, looking up into John's eyes. "Someone is running amuck, making keys to buildings without the owner's knowing. Then he goes and hides them in that one little shop," Sherlock returned to the microscope. "Pray tell, John, how could that not be intriguing?"

"Sorry, how do you define intriguing?" John asked.

"Quiet now, I'm onto something," Sherlock hushed him, and peered into the microscope for about twenty minutes, making mental notes about his findings. Molly had come into the room twice during this time. The first time, Sherlock sent her to get tea, and the second time she was rudely shut out of the room.

"Sherlock, I have a job that needs to be done!" Molly yelled through the locked door.

"Be quiet Molly, I'm working!" Sherlock yelled back. Molly's exasperated groan was very audible through the door and suddenly Sherlock leaped up in achievement. "I've got it!" he cried. John hurried over to his side and Sherlock pointed to the microscope. "Tell me what you see," he demanded.

John stooped over to look into the microscope lens and saw that Sherlock had lined up the two keys so that the teeth fit into each other perfectly, like a puzzle piece. "It took you this long to piece the keys together?" John asked.

"Of course not, I saw that immediately. Look closer, John. What's on the keys?"

John sighed and concentrated on the keys. "I don't see much else," he said, looking up at Sherlock.

"Honestly, John," Sherlock replied, reaching over to zoom the microscope in. "You really must be capable of handling a microscope," Sherlock finished fiddling with the knobs and peered into the lens himself. Satisfied, he pulled back. "Well, go on, take a look."

John looked into the lens once more and something caught his eye. There was a small roughness to the edges of the teeth, making it seem that the keys were cut from the same sheet of metal. There was a very light spot on the tips of both keys, but John didn't know of what.

"Are they the same sheet of metal?" he asked.

"Very good, John," Sherlock praised. "Anything else?"

"Well, there seems to be a sort of spot on the edge, but I can't tell what it is."

Sherlock smiled, but John didn't see, still intently staring at the keys. "It's a chemical called praseodymium. Used in high intensity magnets, high intensity carbon lights, and its salts are used to colour glasses. It's also highly toxic, so be careful."

"What?" John demanded, jumping back from the counter.

"You heard me perfectly, don't be ridiculous, John," Sherlock replied, placing the keys into a small bag. The smile that had decorated his face was erased from existence when John turned to confront him.

"I had a toxic chemical in my pocket?" John demanded.

"Yes."

"Why on Earth didn't you tell me? Wait, don't answer that, I've had enough of you for today," John abruptly said, pulling on his jacket, which he had discarded during the time Sherlock had been staring into the microscope.

Molly finally burst through the door with a spare key she had fetched. "Honestly, Sherlock," Molly said, crossing her arms. "I have stuff I need to get to," she huffed impatiently, and when Sherlock made no movement with the intentions of leaving, she snapped. "Sherlock Holmes!" she bellowed. Sherlock glanced up in surprise;he had not expected her tiny body to make a sound that loud. "Get. Out. Now!" she yelled, pointing an angry finger at the door. "You have overstayed your non-existent welcome, so be a dear and leave."

"I was just on my way out," Sherlock said, collecting his coat and scarf from the floor. He walked up to Molly and leaned over, whispering something in her ear. She nodded slowly and began to bustle about her workplace. "Come along, John," Sherlock called over his shoulder as he left the room.

John gave a disgruntled sigh and followed him out of the lab.


End file.
